In production of semiconductor chips, wafers are fixed on support plates for easy handling and prevention of breakage of wafers during wafer treatment. For example, if a thick wafer, such as a wafer cut out from a silicon single crystal with high purity, is to be grinded into a thin wafer having a predetermined thickness, the thick wafer is bonded to a support plate via an adhesive composition.
The adhesive composition for bonding a wafer to a support plate is required to have high adhesiveness allowing a wafer to be firmly fixed during the step of treating the wafer and to have a property allowing detachment of the wafer without damaging the wafer after the step of treating the wafer (hereinafter, also referred to as “high adhesiveness and easy detachment”).
As an adhesive composition achieving high adhesiveness and easy detachment, Patent Literature 1 discloses a method of treating a wafer by using a double-sided adhesive tape including an adhesive layer that contains a gas generating agent (e.g. azo compound) that generates a gas by stimulation. In the method of treating a wafer disclosed in Patent Literature 1, first, a wafer is fixed on a support plate via a double-sided adhesive tape. In that state, when the tape is stimulated after grinding or the like, a gas generated from the gas generating agent is emitted to the interface between the surfaces of the tape and the wafer, and the pressure of the gas causes at least partial detachment of the interface. The double-sided adhesive tape disclosed in Patent Literature 1 enables detachment without damaging the wafer or leaving the adhesive.
Along with the recent development of semiconductor chips with enhanced performance, wafers are more often subjected to a surface treatment such as a chemical, heating, or exothermic treatment. One of focused techniques for next generation is, for example, 3D stacking technology using through-Si vias (TSVs), in which a plurality of semiconductor chips are stacked to provide a compact device with remarkably high performance. TSVs can provide a high-density semiconductor package and can shorten the connection distance in a semiconductor to achieve low noise and low resistance. TSVs can also achieve remarkably high access speed and excellent release of the heat generated during use. Production of such TSVs requires treatments performed at high temperatures of 200° C. or higher, such as bumping a thin wafer obtained by grinding, forming bumps on the back side of the wafer, and reflowing during 3D stacking.
In the step of treating a wafer including these intensive treatments, a conventional method of treating a wafer as disclosed in Patent Literature 1 may cause reduction of adhesiveness due to the damage on the adhesive composition by a chemical treatment on the surface of the wafer, or may cause reduction of detachability because of enhanced adhesion of the adhesive composition due to high temperatures.